350 Engine - Packaged Performance

One of the keys to the success of the little V-8 is its versatility

Having the most popular performance engine ever built, Chevy small-block owners are lucky indeed. Despite the introduction of the LS engine family (see Modern Mouse elsewhere in this issue), the original Mouse motor continues service in everything from street/strip machines to one-ton work trucks.

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One of the keys to the success of the little V-8 is its versatility. Essentially, it can be tuned for almost any application. Obviously a Camaro owner looking to run in the 11s will choose a different combination than a truck owner looking to haul his favorite bass boat. The great thing about the Chevy is that despite the differences in the application, the basic short-block remains the same. The benefit of this is that just about any buildup, from mild to wild, can start with the very same block, crank, rods, and pistons.

To illustrate this fact, we decided to take your average 350 and subject it to four different performance packages. The idea was to start with a bone-stock engine, then step things up with the proper combination of heads, cam, and intake. The exercise started with an engine producing less than 300 hp but finished up with over 500. Though it is possible to exceed this power output with an engine displacing just 350 cubic inches, 95 percent of street/strip small-block buildups fall between the proposed power outputs.

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Before getting to the particular combinations, it is important to cover something we call shifting the torque curve. Time was when the yardstick for a performance engine was 1 horsepower per cubic inch. Applied to our 350, that would equate to an even 350 horsepower. We know from experience that it is possible to greatly exceed this specific output; in fact, race motors have been known to more than double it. Most street (and strip) motors fall well short of dedicated race motors, achieving somewhere near 1.5 horsepower per cubic inch. The power output of the motor is a function of its ability to process air—the more air in (actually through) the motor, the more power out. Things like high-flow intakes, cylinder heads, and wilder cam timing naturally play a part, but so too does engine speed. Nearly all of the modifications to a stock motor increase the engine speed (rpm) where the motor makes peak power.

The downside to this shift in the power curve is that the sizeable gains offered in middle and upper portions of the curve eventually come with a loss in low-speed torque. Alas, there is no free lunch when it comes to maximizing power production. With that in mind, check out the different combinations and see which one might be right for you.

6 Equipped with the 882 iron heads, cam, and Q-Jet intake, the stock 350 produced 279 hp at 4,500 rpm and 385 lb-ft of torque at 3,300 rpm.

7Graph 1: Stock 350 Starting with a basic 350 with flat-top pistons, we first equipped it with a stock hydraulic flat-tappet cam (the engine was rated at 180 net hp when new), a set of stock iron 882 heads, and Q-Jet intake and carb. Not surprisingly, these stock components produced plenty of torque (385 lb-ft at 3,300 rpm) but very little peak horsepower (just 279 at 4,500 rpm). That the peak power came at just 4,500 rpm was a clear indication that the stock heads, cam, and intake were all designed with low-speed torque in mind. There are obviously more powerful factory cam profiles (the Duntov 30-30 for instance), but we chose these specs to represent what you might find in a fullsize car or truck at your local wrecking yard.

8 Our first upgrade included porting the 882 heads and stepping up to a larger 2.02/1.60 valve package.

9 In keeping with the mild theme, we chose a PE246H cam from the Comp Cams catalog. The PE246H was an emissions-legal cam upgrade for 1987-and-earlier small-blocks.

10 The final components included an Edelbrock Performer RPM Air Gap intake and 650 Demon carb. The ported stock heads with bigger valves, mild cam, and induction upgrade improved the power output from 279 hp and 385 lb-ft to 364 hp and 422 lb-ft. The performance package improved the power output through the entire rev range.

11 Graph 2: 350 Chevy— Stock vs. Upgrade 1 The first upgrade performed to the 350 was to replace the stock cam with what is commonly called an RV grind (Comp PE246-0.429/0.438 lift, 203/212 duration, and 110 LSA). To the cam swap we added a set of mildly ported 882 heads (2.02/1.6 valves) and a Performer RPM Air Gap and Demon 650 carb. The mild upgrades improved the power output substantially, and the power improved throughout the rev range. It goes to show what can be accomplished while retaining the stock heads. The PE246 cam is pretty mild for a 350.

12 The next performance package for our 350 included a set of aluminum 190cc heads from Procomp Electronics. The as-cast heads were not only affordable, they flowed significantly better than our ported stock heads.

13 The aluminum heads were once again teamed with the RPM Air Gap intake, though we replaced the Demon carb with a 650 Holley.

14 To take full advantage of the additional head flow, we installed a slightly wilder cam profile. According to Comp Cams, the XE268H is the favorite small-block performance cam, offering the ideal combination of performance and driveability.

15 Run with the aluminum heads, XE268H cam, and Edelbrock intake, the 350 pumped out 420 hp at 5,600 rpm and 444 lb-ft of torque at 3,900 rpm. Note that horsepower was up by 56, while peak torque improved by just 22 lb-ft. We were starting to shift the curve.

16 Graph 3: 350—Stock vs. Upgrade 2 Upgrade 2 consisted of a set of 190cc as-cast aluminum heads from Procomp Electronics, a slightly wilder (though perfectly streetable) XE268H cam, and Performer RPM Air Gap intake. Replacing the factory Q-Jet was a Holley 650 carb. If your engine spends most of its time below 4,500 rpm, the factory Q-Jet intake works very well. The aluminum version is obviously desirable for the weight savings, but the Air Gap is significantly better at higher engine speeds. Obviously the aluminum heads from Procomp Electronics handily outflowed the factory castings (even ported 882s) while also increasing the compression ratio thanks to 64cc combustion chambers. A perennial favorite among Chevy owners, the Comp XE268H cam offered a 0.477/0.480 lift split, a 224/230 duration split, and the same 110-degree LSA as the previous PE246H cam. The combination of aluminum heads, XE268H cam, and RPM Air Gap intake netted impressive results. The peak power of this combination checked

17 For the final package, we installed a set of 195 Eliminator heads from Air Flow Research. Wanting to maximize airflow and power, we stepped up to the available Competition version.

18 Thanks to extensive CNC porting and a 2.08 intake valve, the AFR Eliminator heads flowed over 300 cfm (enough to support in excess of 600 hp).

19 Replacing the XE268H cam was a serious stick in the form of an XR300HR. The retrofit hydraulic roller offered a 0.562/0.580 lift split, a 248/254 duration split, and 110-degree LSA. This would be considered a wild cam for a street small-block displacing 350 cubic inches.

20 The ARF heads and Comp Hydraulic roller cam were teamed with a new Titan single-plane intake manifold. Like the heads and cam, the intake was designed to maximize power higher in the rev range.

21 Run on the dyno, this final performance package produced 542 hp at 6,300 rpm and 477 lb-ft of torque at 5,100 rpm. With this final combination, we improved the power output by 263 hp and 92 lb-ft from stock and shifted where the motor made peak power (and torque) by 1,800 rpm.

22 Graph 4: 350 Stock vs. Upgrade 3 This is where things start to get serious. The output suggest that this buildup was the most successful, but only if you go by peak power alone. The upgrades included a set of AFR 195 Eliminator heads (competition version), a wild XR300HR hydraulic roller cam (0.562/0.580, 248/254 duration, and 110 LSA), and new AFR Titan composite intake. Equipped as such, the 350 produced 542 hp and 477 lb-ft of torque. Impressive to be sure, but the motor didn't really come on the cam until the tach needle passed 4,500 rpm. This combination would be much more at home on the strip than on the street. This combination pushed the peak power output to 6,300 rpm, up from 5,600 with the previous package. Basically the power gains come from effectively shifting the torque curve higher in the rev range. The downside to the extra power is usually a low in low-speed torque. Combine the AFR 195 heads with a milder cam and a solid dual-plane intake (AFR has a composite dual-plane in

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